AES E-Library

AES E-Library

Improved Low Frequency Microphone Testing

Testing of directional microphones under free-field conditions at low frequencies is problematic if an anechoic chamber is used beneath its cutoff frequency. In accordance to IEC 268-T4 guided waves in a correctly terminated duct can be used to produce a plane, travelling wave at low frequencies. An active absorber system is introduced which reduces the length of the tube and improves the reflection coefficient. First measurements in a test setup are presented.